Baghdad, Iraq (CNN) -- U.S. troops shot and killed an Iraqi man at Baghdad International Airport on Sunday morning, a U.S. military spokesman said.

A military convoy attempted to stop the man, who they spotted driving a vehicle at high speed on an airport road, Col. Barry Johnson said.

"The vehicle was perceived as a threat and a decision was made to engage it with small-arms fire in order to stop it and to protect the convoy from a possible attack," Johnson said.

The driver did not respond to U.S. hand signals before troops opened fire, he said.

Baghdad police said the man was an engineer working at the airport. They did not name him.

Authorities are investigating the incident, Johnson said.

CNN's Mohammed Tawfeeq in Baghdad contributed to this report.